1. Field of the Invention:
This invention relates to a method for manufacturing cold rolled, nondirectional electrical steel sheet and strip.
2. Description of the Prior Art:
Since cold rolled, nondirectional electrical steel sheet and strip is used chiefly for rotary electrical instruments, it is desirable that the sheet have uniform magnetic characteristics with no distinct orientation in any direction within the plane of the sheet or strip (hereinafter referred to as sheet).
In the mass production of such electrical steel sheet which possesses essentially uniform magnetic characteristics in all directions in the plane of the sheet, technical efforts have hitherto been made to orient the crystals constituting the steel sheet in a random direction.
However, alloy steels, such as, carbon steel, silicon steel, and aluminium steel for use as electrical steel sheet are constituted of .alpha.-phase, i.e., crystals having body centered cubic lattice at room temperature, and as it is well known, it is most difficult to obtain magnetization of the direction described as &lt;111&gt; by means of Miller's notation.
Conventional cold rolled, nondirectional electrical steel sheets comprising crystals having a random direction contain many crystals having the direction of &lt;111&gt; as the direction of magnetization. Accordingly, although they are non-orientating, they have only a relatively low magnetic flux density in all directions.
On the other hand, methods for manufacturing electrical steel sheet having a crystal orientation so as to contain many crystals having &lt;100&gt; direction which is favourable for magnetization in the plane of the sheet, i.e., two-directional electrical steel sheet composed of crystals having the orientation of (100)[001] described by Miller's notation, or the so-called "poly-directional" electrical steel sheet comprising crystals having the orientation of (100) [OKl] have been proposed. However, many of these are not suitable for mass production, because the manufacturable grades are restricted due to the limitations in the components or to the very precise treatment required in the course of manufacture.